Encapsulation processes have been developed to make capsules containing a selected ingredient or mixtures of ingredients coated with a layer of another composition. Capsules can be made in many sizes. Small capsules come in various size ranges from about 1 micron to several millimeters. The smallest capsules can be used in emulsion formulas. The smaller capsules are sometimes referred to as microcapsules.
Some microcapsules are designed to break under pressure so that the internal ingredient is released when rubbed over a surface. Microcapsules have been made containing therapeutic agents to be ingested coated with films broken down because of pH changes in the gastric system. Other films or shells on capsules are soluble in particular solvents. Release of the internal component is controlled generally by solubility characteristics and the thickness of the shell.
The microcapsules are made by methods well known in the art and have been used in numerous industrial and commercial applications. Typical processes are centrifugal extrusion, pan coating and air suspension methods. U.S. Pat. Nos. 3,692,690; 3,015,128 and 3,310,612 are exemplary of encapsulation techniques known and practiced in the art. In addition to those illustrated by the patents, other techniques are available. The present invention can utilize any of the available methods for preparing capsules or microcapsules.